Difference between revisions of "Definitions"

Revision as of 22:04, 6 October 2015

Aperture Controls how much light can go through the lens and sensor. 

Resolution The resolution of a camera is often limited by the image sensor that turns light into discrete signals. The brighter the image at a given point on the sensor, the larger the value that is read for that pixel.

IR LEDs Illuminates image in the night. Infrared light emitted by the light, wavelength of 850nm and 940nm, are not visible , energy saving, the past 10 years, it has been widely used in the field of security monitoring

Min Illumination Minimum illumination is a parameter to show the camera‘s performance in the night or low light scene. The smaller the value is ,the higher the sensitivity of the sensor is.

MJPEG Motion JPEG (M-JPEG or MJPEG) is a video compression format in which each video frame or interlaced field of a digital video sequence is compressed separately as a JPEG image.

H.264 The intent of the H.264/AVC project is to create a standard capable of providing good video quality at substantially lower bit rates than previous standards, without increasing the complexity of design so much that it would be impractical or excessively expensive to implement.

H.265

Bitrate Byte transfer speed for every second it transfers. The unit is bps(bit per second).The higher the bitrate is, the more data it can transfer.

Variable Bit Rate(VBR) without a fixed bit rate, in the compression software, determined by the instant video data bit rate, quality taking into account.

Constants Bit Rate(CBR) fixed sample rate compression. The advantage is fast compression, can be supported by most software and device, the disadvantage is the relatively large space

I Frame Interval the interval time between every two I frame, I-frame is called intra-picture, P-frame is called prediction picture. I-frame need more space and the best image quality.

PreRecord You can set pre-record time(from 1-30s), this function can extend the life of HDDs and help to analysis MD/Alarm video( you can refer the event part )

POE -Power over Ethernet. By this technology, we could transmit the network signal not only with single cable, but also the power supply. (MAX. Distance 100 Meter)

ONVIF/PSIA These protocol regulate the function of application interface. By these protocol, not only DAHUA IPC could be accessed to DAHUA NVR, but also others brands that support ONVIF or PSIA. And all over network devices, which support ONVIF or PSIA, could communicate each other.

EIS Electronic image stabilization

IVS Estimate the camera’s internal parameters (including internal geometric features, optical features) and external parameters (the camera’s 3D location and direction relative to the real coordinate system) according to one horizontal line and three altitude lines calibrated by users, then confirm the corresponding relations between the 2D image captured by the camera and real 3D object.

Tripwire Function Only applied to the scene where the targets are sparse and there is rarely any covering between targets, such as the perimeter without any guard. It will trigger alarm when the target passes through the warning line according to the set movement direction. It takes some time from the target appears to the target is confirmed, so it needs to leave some space when setting warning line, do not set it near the covering. Detect if there is any object crossing the warning line, it can support different direction selection, such as A->B, B->A and bidirectional, and it can activate record , snapshot and alarm according to the judgment result.

960H 960H is a new video standard for security systems that provides high resolution images using new advanced image sensors. Security cameras capable of 960H produce an image that is 960x480 compared to 702x480 for D1 and 352x240 for CIF.

HD-CVI In November 2012, Dahua technology released analog high-definition transmission interface technology-HDCVI（High Definition Composite Video Interface）, with self-owned intellectual property right. HDCVI technology is a HD video transmission method, based on existing SYV75-3 or SYV75-5 coaxial cable. It can achieve long distance HD video signal reliable transmission at low cost via low general coaxial cable. In the practical application, HD-SDI subsystem requires high transmission medium, while HDCVI is suitable to the long distance, low cost transmission medium and complex deployment situation.

ONVIF A global and open industry forum with the goal to facilitate the development and use of a global open standard for the interface of physical IP-based security products. Or in other words, to create a standard for how IP products within video surveillance and other physical security areas can communicate with each other

IP Cam (Network Camera) A network camera can be described as a camera and computer combined in one unit. The main components of a network camera include a lens, an image sensor, one or several processors, and memory. The processors are used for image processing, compression, video analysis and networking functionalities. The memory is used mainly for storing the network camera’s firm- ware (computer program), but also to store video for shorter or longer periods of time.

LAN(Local Area Network) A local area network (LAN) is a group of computers and associated devices that share a common communications line or wireless link. For example, an enterprise network is generally a local area network. A network of large-scale video surveillance project is a local area network.

TCP/UDP These protocol regulate the transmission method of network signal of IP equipments. By these protocol, we realized our DAHUA IPC to access our DAHUA NVR, and all over the DAHUA network devices could communicate each other.